Improvements in microelectronics have increased the demand for electrolyte battery cells, such as Li-ion and/or Li-ion polymer cells, that can be directly incorporated into electronic devices so as to produce a portable, self-contained product. Some of these products are designed such that the battery cell may be attached directly to an electronic circuit within the product.
Broadly stated, a Li-ion and/or Li-ion polymer cell is generally comprised of a plurality of layered sections, namely, an anode section, a cathode section and a separator layer that is disposed between the anode section and cathode section. Multi-layered cells are comprised of a plurality of anode sections and cathode sections.
Each anode section and each cathode section includes a layer of a conductive material that is disposed within or in contact with such section. This layer forms what is conventionally referred to as a “current collector.” It is conventionally known to use metal screens or meshes or foils to form the aforementioned current collectors. Typically, copper mesh is used to form an anode current collector, and an aluminum metal mesh is used to form a cathode current collector. Multi-layered cells typically include a plurality of anode current collectors and a plurality of cathode current collectors. Each current collector generally includes an outwardly extending, short tab that is ultimately to be connected to a battery lead. Battery leads are typically comprised of a flat metallic strip, formed of copper, aluminum or nickel. It is, therefore, necessary to join all anode current collectors together and attach them to a single anode lead. Likewise, all cathode current collector tabs must be joined together and attached to a cathode lead.
Typically, multi-layered cells are comprised of “bi-cells” that are stacked together. A bi-cell typically includes an anode section disposed between two cathode sections. Thus, such batteries have twice as many cathode current collectors as anode current collectors. For example, it is not unusual for multi-layered cells to have ten or more cathode current collector tabs that must be joined together and attached to a cathode lead. Such a battery would require that five or more current collector tabs be joined together and attached to an anode lead.
Since the anode current collector tabs and the cathode current collector tabs and their connections, respectively, to an anode lead and a cathode lead, necessarily occur within a battery package, the area within the battery allotted to this assembly reduces space for active battery material. Accordingly, it is highly desirable to minimize the space utilized in joining current collector tabs and leads within a battery package.
The present invention provides a method of joining current collector tabs and battery leads and a structure formed thereby.